Dewatering gluten with anionic surfactants

ABSTRACT

Methods of enhancing the dewatering of gluten are disclosed. The methods comprise adding an anionic surfactant to the wet gluten prior to dewatering, as in vacuum dewatering equipment. Particularly effective surfactants are sulfates and sulfonates.

FIELD OF THE INVENTION

The present invention is directed to a method of improving thedewatering of gluten in grain processing. More specifically, the presentinvention is directed to the use of anionic surfactants to enhance thedewatering activity of vacuum dewatering equipment employed in corngluten processing.

BACKGROUND OF THE INVENTION

The present invention relates to the dewatering of gluten during cornprocessing. The wet milling processing of shelled corn is employed toobtain staple products such as corn oil, dextrose, corn syrup, highfructose corn syrup, dextrins, dry starches and feeds. The principalsteps in the wet milling of corn include steeping, milling, recoveringand processing. During the steeping operation, corn kernels are softenedby soaking in a hot dilute solution of sulfurous acid (i.e., sulfurdioxide). The softened kernels are then passed through grinding millsand separators where the germ is removed and the starch and gluten areseparated from the coarser hull and fibers. The starch is then separatedfrom the gluten which is added to the fibrous material and processedinto a high protein animal feed. The starch is recovered as dry starchor further processed into dextrose and fructose. The sulfurous acidsteepwater initially used to soften the corn contains solubles which arerecovered for use in feeds. The steepwater solids are recovered byevaporation and drying. The solids recovered from evaporating and dryingthe steepwater are used as additives to livestock feeds to enhance theirnutritional value.

Processing of the gluten also involves dewatering. Typically, the glutenstream is held in a light gluten storage tank prior to pumping to a bowltype centrifuge where the first step of dewatering begins. The glutenslurry from the centrifuge, called heavy gluten, is then sent to avacuum dewatering system where the second step in the dewatering occurs.The gluten cake from the vacuum dewatering system is transported byauger to a dryer for final dewatering.

In the gluten dewatering process, the second step of vacuum dewateringis often the limiting factor in gluten recovery. The time necessary toreach the required gluten moisture content coupled with the potentialfor blinding of the filter media limits the throughput of gluten in thisarea. The present invention is directed to a process for decreasing theproduct cake moisture in the gluten dewatering process.

The use of surfactants in grain processing is known. U.S. Pat. No.3,362,829 discloses a process for coating powdered vital wheat glutenwith a nonionic hydrophilic lipid selected from the class consisting ofmonoglycerides, salts of lactylic esters of fatty acids, polyoxyethylenestearate and stearyl monoglyceridyl citrate. The coating of the powderedwheat gluten with such nonionic hydrophilic lipids is disclosed ascontrolling wetting of the vital wheat gluten upon hydrogenation. Theuse of polyoxyethylene sorbitan monostearate in combination withhydrophilic lipids is also disclosed. The surface active agent, i.e.,polyoxyethylene sorbitan monostearate is included as an aid for theinitial dispersion of the vital wheat gluten.

U.S. Pat. No. 3,880,824 discloses a gluten/lipid complex and process forpreparing a gluten/lipid complex in which vital wheat gluten complexeswith lipids are prepared which are resistant to particle cohesion. Afinely divided vital wheat gluten is reacted with ionic and nonionicfatty substances selected from the group consisting of fatty acidchlorides, fatty monoglycerides, lactylic esters of fatty acids,phospholipids and sorbitan fatty acid esters in the presence of a mildbase catalyst. The phospholipids and lactylic esters of fatty acidsyield comparable complexes in an acidic environment.

U.S. Pat. No. 4,929,361 discloses a method of controlling the fouling ofheat transfer surfaces in evaporators and concentrators employed in wetcorn milling which comprises treating the wet corn solution with anonionic surfactant such as polyoxyethylene 20 sorbitan R.

U.S. Pat. No. 5,283,322 discloses a method of improving the dewateringof gluten, e.g. gluten from the corn wet milling process, through theaddition of nonionic surfactants to the process stream.

SUMMARY OF THE INVENTION

The present invention provides a process to enhance the removal of waterfrom wet gluten in a gluten dewatering operation. The present inventordiscovered that the addition of an anionic surfactant to a wet glutenstream prior to dewatering enhanced the dewatering ability of vacuumequipment. Particularly effective at enhancing vacuum dewatering aresulfates and sulfonates.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present inventor discovered that surfactants and more particularlyanionic surfactants effectively enhance the dewatering of gluten invacuum dewatering equipment. Typically, in the processing of corn glutenthe dewatering operation is the limiting factor in gluten recovery.Conventionally, the dewatering of gluten is a multiple step operationcomprising centrifuge dewatering followed by vacuum dewatering andthereafter drying. The vacuum dewatering equipment limits glutenproduction rates due to the time consuming nature of the operation.

It has been discovered that adding anionic surfactants, particularlysulfates and sulfonates, at concentrations of 100 to 2500 ppm (based ontreatment actives content and the dry solids content of the glutenslurry) enhances the efficiency of the mechanical dewatering process byreducing the gluten effluent moisture. Laboratory tests demonstratedthat this moisture can be reduced by approximately 1 to 2% absolute,which translates to a process energy reduction of 225 to 475 BTU perstandard bushel of corn, assuming typical wet milling process yields.While efficacy at dosage levels below 100 ppm was not tested, it isanticipated that an improved dewatering effect of these treatments wouldoccur. The level of treatment dosage will depend on the particular corngluten slurry being treated.

EXAMPLES

All tests were conducted using process samples provided by a major U.S.corn wet milling facility. Samples were composed of concentrated glutenslurry after the dewatering centrifuge and before the rotary vacuumfilter.

A standard filter leaf test apparatus was used to simulate the rotaryvacuum filter. The media assembly was modified to allow filter paper tobe used instead of filter cloth. This eliminated any potential residualeffect in sequential treatment testing, as well as gradual fouling ofthe cloth with proteins in the gluten.

The experiments consisted of placing the gluten slurry sample atapproximately 110° F. into an agitated beaker. The vacuum level wasestablished at 17" Hg. The beaker agitation was stopped, and the mediaassembly inserted into the gluten. After allowing 30 seconds for thecake to form, the assembly was removed from the beaker and inverted toallow drainage of filtrate from the assembly. Vacuum was maintained foran additional 30 seconds to simulate the cake drying time found inindustrial rotary vacuum filters. The cake was then analyzed for percentmoisture using a standard oven method. Experimental results are shown inTables I and II, below. Note that negative values may be attributable toe.g., adhesion of free starch to the fiber, daily variations in thecontrol (untreated) data, etc.

                  TABLE 1                                                         ______________________________________                                        Effect of Sulfates on Gluten Filter Cake Moisture                                                        Moisture Reduction                                 Treatment      Dosage (ppm)                                                                              (Control-Treated, %)                               ______________________________________                                        sodium alkyl aryl                                                                            500         0.73                                               polyether sulfate                                                                            2500        1.16                                               sodium 2-ethyl-1-hexyl sulfate                                                               100         -0.34                                                             250         -0.02                                                             500         1.36                                                              2500        1.59                                               sodium dodecyl sulfate                                                                       100         1.62                                                              250         0.30                                                              500         1.44                                                              2500        0.71                                               ______________________________________                                    

                  TABLE II                                                        ______________________________________                                        Effect of Sulfates on Gluten Filter Cake Moisture                                                        Moisture Reduction                                 Treatment      Dosage (ppm)                                                                              (Control-Treated, %)                               ______________________________________                                        sodium linear  100         0.18                                               alkylbenzene sulfonate                                                        magnesium sulfonate                                                                          250         -0.79                                                             500         1.41                                                              2500        1.62                                               sodium hexadecyl diphenyl                                                                    250         -0.21                                              ether disulfonate                                                                            500         1.63                                                              2500        0.66                                               sodium sulfonate                                                                             100         0.40                                                              500         0.79                                                              2500        1.81                                               sodium octyl sulfonate                                                                       100         1.15                                                              250         0.36                                                              500         0.90                                                              2500        0.63                                               sodium α-olefin sulfonate                                                              500         0.18                                                              2500        1.09                                               sodium dodecylbenzene                                                                        500         0.38                                               sulfonate      2500        0.54                                               α-olefin sulfonate                                                                     250         -0.67                                                             500         0.64                                                              2500        1.35                                               ______________________________________                                    

These tests indicate that anionic surfactants, particularly sulfates andsulfonates, at dosages o 100 to 2500 ppm (based on treatment activescontent and the dry solids content of the gluten slurry) are effectivein reducing the effluent cake moisture in corn gluten rotary vacuumfilters by approximately 0.5 to 2.0 percent. Sulfates and sulfonatesappeared to be the most effective anionic surfactants in improving thedewatering of gluten in laboratory tests. The sulfates and sulfonateslisted should be considered representative of sulfates and sulfonates ingeneral and should be regarded solely as illustrative withoutrestricting the scope of the invention.

Sodium dodecyl sulfate (commonly referred to as sodium lauryl sulfate)and sodium octyl sulfonate yielded cake moisture reductions at dosagesas low as 100 ppm active, dry solids basis. Sodium 2-ethyl, 1-hexylsulfate, at dosages of 500 and 2500 ppm reduced filter cake moisturenearly as much as sodium dodecyl sulfate at 100 and 500 ppm. Sodiumalkyl aryl polyether sulfate, sodium hexadecyl diphenyl etherdisulfonate, and α-olefin sulfonate also demonstrated efficacy atvarious concentrations.

Additional anionic materials were tested. Results are found in TableIII, below.

                  TABLE III                                                       ______________________________________                                        Effect of Other Anionic Materials on Starch Filter Cake Moisture                                         Moisture Reduction                                 Treatment      Dosage (ppm)                                                                              (Control-Treated, %)                               ______________________________________                                        dioctyl sodium sulfosuccinate                                                                500         -0.35                                                             2500        0.21                                               phosphated mono- and                                                                         100         -0.87                                              di-glycerides                                                                 N-lauroyl, N, N.sup.1, N.sup.1 -                                                             500         0.57                                               ethylenediaminetriacetic acid                                                 ______________________________________                                    

While this invention has been described with respect to particularembodiments thereof, it is apparent that numerous other forms andmodifications of this invention will be obvious to those skilled in theart. The appended claims and this invention generally should beconstrued to cover all such obvious forms and modifications which arewithin the true spirit and scope of the present invention.

I claim:
 1. A method of enhancing the dewatering of gluten whichcomprises adding to an aqueous gluten solution prior to dewatering, aneffective dewatering amount of an anionic surfactant.
 2. The method asrecited in claim 1 wherein from about 100-2500 ppm of the anionicsurfactant is added to the aqueous gluten solution prior to dewatering.3. The method as recited in claim 1 wherein said anionic surfactant is asalt of a sulfonic acid or a sulfuric acid ester.
 4. The method asrecited in claim 3 wherein said sulfuric acid ester salt is selectedfrom the group consisting of a sodium alkyl aryl polyether sulfate and asodium alkyl sulfate.
 5. The method as recited in claim 4 wherein saidsodium alkyl sulfate is sodium dodecyl sulfate or sodium 2-ethyl-1-hexylsulfate.
 6. The method as recited in claim 3 wherein said sulfonic acidsalt is selected from sodium hexadecyl diphenylether disulfonate and asodium alkylbenzene sulfonate.
 7. The method as recited in claim 3wherein the anionic surfactant is a magnesium or sodium salt of asulfonic acid.
 8. A method of enhancing the vacuum dewatering of wetcorn milling gluten which comprises adding to the wet corn millinggluten, prior to vacuum dewatering, an effective dewatering amount of ananionic surfactant.
 9. The method as recited in claim 8 wherein fromabout 100-2500 ppm of the anionic surfactant is added to the aqueousgluten solution prior to dewatering.